With respect to a biometric authentication technology, it is demanded that a distance between an object and a sensor is in an appropriate range during taking an image of the object, when a sensor having a camera captures a biometric image without contacting. Therefore, a guide is often used in order to correct a posture of the object or a height of the object from the sensor. However, in a case where a biometric authentication is performed with a mobile terminal, portability is degraded when the guide is used. And so, it is demanded that the distance between the object and the camera is detected from the biometric image and the object is induced to an appropriate height.